We have a Geneva Convention, and international norms against nuclear weapons, which are also pretty good deterrents themselves (we hope).

Just like nuclear powers sometimes wage limited conventional wars, it's possible to imagine a set of international laws and norms where disputes would be resolved by virtual conflicts without escalation to armed force.

Advances in robotic war machines could make them so fearsome they deterred real-world armed conflict in favor of virtual conflict. (Of course, that's what they said about the machine gun before WW1)

The Geneva Convention only works if both sides abide by it. Such deterrents only work because we allow them to work. Once one side decides the consequences of going against the norm is acceptable, or can be avoided altogether, then the rules no longer apply.

What makes you think that disabling infrastructural targets will result in fewer casualties?

Power for heating, cooling and hospitals. Transit systems for food distribution. Computers for synchronising all of the above.

How many casualties do you think would result from shutting down infrastructure in NYC in mid winter?

Even evacuation causes casualties. I was reading an assessment of the Fukushima evacuation that suggested fewer casualties would have resulted from just staying there.

Blowing up all transformers in the power grid by inducing a huge power surge surely causes fewer casualties than blowing up all transformers using bombs.

Perhaps?

I suspect the random variation between the two would account for far more difference than the casualties directly attributable to method of destruction, though.

Unless you mean destroying the transformers with blockbuster-size HE, or dirty nuclear devices?

I guess my point is that the number of people who would die from sustained, widespread infrastructure disruption would be huge, and not greatly changed by casualties around the blast site if you decided to blow stuff up literally instead of just metaphorically.